Population characteristics of Dipper Cinclus cinclus roosts in mid and south Wales
Titel:
Population characteristics of Dipper Cinclus cinclus roosts in mid and south Wales
Auteur:
Ormerod, S. J. Tyler, S. J.
Verschenen in:
Bird study
Paginering:
Jaargang 37 (1990) nr. 3 pagina's 165-170
Jaar:
1990-11
Inhoud:
Previous studies of Dippers Cinclus cinclus revealed that, although they are territorial and feed in a solitary way, groups of several individuals sometimes gather at roosts. We assessed the relative frequency of group roosting from 307 visits spread across the year to 98 bridge roosts. Although 9 birds were present at some sites, the majority of sites held only 1 bird. For much of the year, most birds roosted in 'pairs' consisting more often than expected of a male and a female. Sex ratios were around 1:1 in roosts of all sizes, though first years made a proportionately greater contribution to larger roosts. Roost size increased during the winter probably because birds from natural sites moved to bridge sites. The latter probably offered warm conditions during a cold period. While these features suggest some meteorological influence on roosting behaviour, the numbers of birds roosting at each site could be explained in part by the number of niches available, the local density of Dippers able to fill them, and the distance to alternative locations.
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